Sensors For Automotive Applications

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1 © 2014 ANSYS, Inc. March 13, 2015 ANSYS Confidential

Sensors for Automotive Applications

ANSYS, Inc.


Introduction

Hall Sensor

Variable Reluctance Sensor

Magneto-resistive Sensor

Flux Gate Sensor

Eddy Current Sensor

Summary

Contents


Sensors are electromechanical devices that use magnetic field for sensing

Velocity sensors for antilock brakes and stability control

Position sensors for static seat location

Eddy current sensors for flaw detection

Introduction


Use specific magnetic solvers to understand the basic physics of the sensor• Vary Geometry, Material Properties, Environmental

Conditions• Understand Key Factors that most Significantly affect

Performance– Statistical, Monte Carlo, Sensitivity, Design of Experiments

• Use Optimization Tools to Refine Design– Quasi-Newton, Genetic, Pattern Search

• Create a Model of the Sensor for use in System Simulation

Component Analysis


Use System Simulation to understand the Sensor’s impact on the whole system• Design a robust sensor using appropriate technology• Don’t Over-Design unnecessarily• Consider Variations

System Analysis


• For speed control• Determine flux passing through 3D

Hall effect sensor• Rotate sensor and vary gap

Hall Effect Sensor

Gap between pole piece and target wheel

Rotate about the Z axis through one half of a tooth, or 30 degrees.

Permanent magnet

Pole piece

Hall sensors

IC chip


Flux in Hall effect sensor can be determined by integrating B(normal) on a surface

Hall Effect Sensor

Field in permanent magnet & pole piece

Field in IC and Hall sensor


Hall Effect Sensor – Meshing Tips

Sensor Air BoxRequired for Proper Meshing

Target Air BoxRequired for Proper Meshing


Differential Hall Sensor

Gap between pole piece and target wheel

Target Wheel

Permanent

Magnet

Pol

e P

iece

Cell Top

Cell Bot

Hall IC

21

cell_face

aveavediff

xave dAB

ϕϕϕ

ϕ

−=

= ∫


Average top and bottom flux vs. angle

Spacing = 1, 2, and 3mm

Hall Sensor - Parametric Results


Hall Sensor - Simplorer Simulation

ICA:

Link1.GAP := 3

EQU

Difference := FLUXM2.FLUX - FLUXM1.FLUX

FLXFLUXM1 FLX FLUXM2CONST

CONST2

Difference

COMP1ECE

EMSSLink1

ROT

ROT_Vw +

Maxwell 3D LinkMaxwell 3D Link


Spacing = 3mm

Differential signal is too small

Hall Sensor - System Simulation

0.00 100.00 200.00 300.00 400.00 500.00 600.00Time [ms]

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Flux

[vs]

0.0000

0.0010

0.0020

0.0030

0.0040

0.0050

Y2

Curve Info Y AxisFLUXM1.FLUX

TR Y1

FLUXM2.FLUXTR Y1

DifferenceTR Y2

COMP1.VALTR Y2


Spacing = 1mm

Differential signal is detected

Hall Sensor - System Simulation

0.00 100.00 200.00 300.00 400.00 500.00 600.00Time [ms]

0.00

0.03

0.05

0.08

0.10

0.13

0.14

Flux

[vs]

0.00

0.03

0.05

0.07

0.10

0.13

0.15

0.17

0.20

0.21

Y2

Curve Info Y AxisFLUXM1.FLUX

TR Y1

FLUXM2.FLUXTR Y1

DifferenceTR Y2

COMP1.VALTR Y2


For speed control by determining output voltage

Consider varying flux linkage vs. time due to fringing, nonlinear materials, and speed of rotation


Permanent magnet

CoilPole piece



Finite element model

(equivalent circuit)

Output voltage vs. time

Angle vs. Time


• For speed control of gear wheel• Resistance changes with the angles • which the magnetic field which

crosses • the direction of current accomplishes

• Use Maxwell to determine average magnetic field angle: α

• In Simplorer, look-up table of α vs. rotation gives resistance



Input Parameters• Rotation angle of Wheel• Permeability of missing tooth


RotAngle

$TeethMur

Magnetize M


Output Parameters• The Angle of magnetic field on sensor

part

Magneto-resistive SensorSens_Fwd Sens_Back

=

∫∫−

VdvH

VdvH

x

y

/

/tan 1α

Qty ・ H ・Scalar ・ YGeom ・ Sens_Fwd ・ Integ

Qty ・ H ・ Scalar ・ XGeom ・ Sens_Fwd ・ Integ

/

Trig ・ Atan

Constant ・PI ・/Number ・ 180.0 ・*

[Add] → Ang_Fwd

Operation of Calculator.


Exporting Lookup Table– Export as format of Table .– Data is manually processed by other tools. (e.g. Excel)– Reload as Table Export SML.


Export from Parametric Solutions Export from Imported Table

ECE - LINKECE - LINK

編集

Part for One round is copied

Result table file : ±30[deg] and ±15[deg] Result table file :

Merged as Complete one round.


-15[deg] Magnetic Flux Density B

-13[deg] H vector near sensor.



Parametric results – α vs. rotation

Shows results for missing tooth


-15[deg] ~ 15[deg] -30[deg] ~ 30[deg]


-20.40m

20.40m0

0 40.00m20.00m

MRSensor.Sensitivity

Sensor output Voltage.

28.00u

29.00u

28.50u

0 40.00m20.00m

VM1.V [V] + -2.50

-9.92

10.00

0

0 40.00m20.00m

VM6.V [V]

Amplified Output.

System Model with Sensor


System Model for Speed Control

Angle

speed


For static position indication

A fluxgate sensor contains a small core designed to be easily saturated

Inductance is affected by the magnitude of an external field created by drive coil

The value of inductance can change by 10 times or more

This circuit provides an output voltage that is proportional to the magnitude and the direction of an externally applied field.

Fluxgate Sensor

Drive Coil Core


Arrows Indicate Magnetization Direction

Typical Flux Gate Sensor Applications include:• Proximity Sensing• Magnetic Field Measurement (Navigation, Geomagnetics)• Speed & Position Sensing

Sensor has Linear Response Characteristic

Fluxgate Sensor


Arrows Indicate Magnetization Direction

Typical B-H Curve

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-8.0E+05 -6.0E+05 -4.0E+05 -2.0E+05 0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05

H (A/m)

B (T

)

Sensor is Driven Between Linear and Saturated Regions of the B-H Curve

Saturated Region - Low Inductance

Saturated Region - Low Inductance

Fluxgate Sensor Basics


Saturated Region

Linear Region Curve Shifts

Due To Influence of External Field

Parametric Analysis


• Waveform Distortion caused by traversing the B-H Curve

• Positive and Negative Areas are Equal

System Analysis

Cur

rent

(A)

Time (s)


External Field Shifts Curve Positively or Negatively

Positive and Negative Areas are No Longer Equal

Sinusoidal Response

Force = 3.72N

Cur

rent

(A)

Time (s)


Cur

rent

(A)

Time (s)

Square Wave Response


Differential Configuration System Simulation


Differential Flux Gate Sensor System Output Voltage2.50

2.402.41

2.42

2.43

2.44

2.45

2.46

2.47

2.48

2.49

1.00e-003 4.00e-0032.00e-003 3.00e-003

• Differential Sensor Response• External Field For Sensor 2 Changes from 0G to –2G at 2ms• Output Voltage Shifts Downward to Reflect the Change

Differential Results


Current density for unflawed and flawed cases very different

Flaw changes stored energy, and thereby affects mutual inductances of coils

Differential voltage calculated by:

Eddy Current Flaw Sensor

)( 2121 pudpuddriveroc LLNNIV −− −= ω


For flaw detection in structures without altering the physical makeup of that structure

Eddy Current Probes are based on the principle of artificially creating induced current in the target material, from which we are able to detect if any defect is present

Eddy Current Sensor


This is a multi-parametric Eddy Current problem

Goal: sweep the probe at every location on the pipe and reconstruct cartography of the flux patterns

Comparing simulated and tested results allows testers to have a better understanding of the measurements taken in the field

Description of the Task


The tested device is a pipe made of Inconel


22 mm

1.3 mm thick

µ = 1.001

σ = 970,000

Skin depth:

0.6mmδ1.6mmδ

600kHz

100kHz

==


The vertical slot crack blocks all the induced current. This crack should be easy to detect

The horizontal surface crack only alters current paths. This crack is more difficult to detect

Will the probe be able to detect the signal due to the surface crack ?


10 mm


The Probe works at 2 frequencies: 100 kHz and 600 kHz

We need to solve each problem twice

Note: this is not the exact geometry used by customer


SourceCoil

Pick up Coils


Maxwell set up:• Solve the design with the crack as

vacuum• Duplicate the design• Change material property of crack to

inconel (to remove the crack) in the second design

• Solve the second design without adaptive meshing, importing final mesh from original design

Solve twice with same mesh


Induced Currents

Results


Several examples of sensors were given including: • Hall, VR, Magneto-resistive, Flux Gate, and Eddy Current

These were used for speed, position and flaw sensing

Both component and system level simulations were necessary to understand the coupling interaction and complete performance of most sensors

Summary

Sensors For Automotive Applications

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